Auditory, Vestibular, Olfaction, and Taste Systems Flashcards
auditory system gross anatomy
otic capsule gross anatomy
what is the membranous labyrinth filled with
endolymph, which has a higher potassium concentration and lower sodium concentration
what is the bony labyrinth filled with?
perilymph, resembles extracellular fluid and CSF
how is the membranous labyrinth contained in the bony labyrinth?
suspended within it by spiral ligament and delicate filaments
how sound waves move through gross auditory system
sound waves vibrate tympanic membrane
vibrations transmitted through ossicles of middle ear
base of stapes vibrates at oval window
pressure waves in the perilymph of scala vestibuli
displacement of basilar membrane of the cochlear duct, bending hair cells of organ of Corti to stimulate action potentials
vibrations transferred across cochlear duct to perilymph of scala tympani
pressure wave dissipated by secondary tympanic membrane at the round window
where is the organ of Corti located?
within the cochlear duct that is between the vestibular and tympanic canal
what kinds of hair cells are found within the organ of Corti?
inner and outer hair cells
what are inner hair cells? what do they do?
single row of hair cells innervated by up to 10 nerve fibers
detect frequency and fine discrimination of sounds
what are outer hair cells? what do they do?
efferent structures of 3 to 4 rows, with 1 nerve fiber reaching multiple cells
modulate sensitivity of organ of Corti by changing their length in response to sounds
can hair cells heal?
no! cannot regenerate either
how are sound frequencies organized in the cochlea
low frequencies at the tip of the apex, high frequencies at the base
how can hearing loss occur?
can be selective where a certain part of the cochlea is damaged, would only experience hearing loss for certain frequencies
where are cell bodies for the primary sensory neurons of sound located?
the spiral ganglion
auditory pathway, DCN
neurons sent to dorsal cochlear nucleus at pontomedullary junction
decussate after dorsal cochlear nucleus and ascend in the lateral lemnicus to inferior colliculus
from inferior colliculus, bilateral projections go to medial geniculate nucleus
from MGN, project to primary auditory cortex as auditory radiations
where is the primary auditory cortex
anterior transverse temporal gyrus
auditory pathway, VCN
neurons to ventral cochlear nucleus
from VCN, bilateral projections to superior olivary nuclear complex
from SONC, bilateral projections to inferior colliculus
from IC, bilateral projections to medial geniculate nucleus
from MGN to primary auditory cortex via auditory radiations
what does the superior olivary nuclear complex do?
functions in localizing sounds horizontally in space
where do auditory fibers decussate?
trapezoid body
this intersects with the medial lemniscus
where will a lesion be for there to be unilateral auditory symptoms?
cochlear nuclei or nerve
past the cochlear nuclei, what would a lesion of the auditory system cause?
issues localizing and interpreting sound
what artery supplies the cochlear nuclei?
AICA
some neurons in the superior olivary complex project back to where? why?
to the cochlea
to influence the basilar membrane via outer hair cells
where are the secondary and higher-order auditory cortices located? what activates them?
around the primary auditory cortex, forming a belt
activated by complex sounds
what are the 5 vestibular sensory organs in the vestibular labyrinth?
utricle and saccule (linear acceleration and gravitational positioning)
3 semicircular canals (angular acceleration)
what are the utricle and saccule?
ovoidal sacs of membranous labyrinth, full of endolymph
what is the macula of the vestibular system?
patch of hair cells in each organ, covered by otolithic membrane
what is the otolithic membrane?
gelatinous sheet covered in otoliths (calcium carbonate particles)
what does motion of the head cause?
shifting of the otolithic membrane, deflects the hair bundles and excites the hair cells
what do the utricle and saccule detect
utricle - horizontal acceleration
saccule - vertical acceleration
what do semicircular canals respond to
rotational motion in one of three rotational planes - movement of endolymph only
what is the cupula
gelatinous diaphragm that interrupts the endolymphatic space at the ampulla of each semicircular duct
what excites the cupula
movement of endolymph against the cupula excites the hair bundles that penetrate the cupula
medial longitudinal fasciculus
bilateral connections with CN III, IV, VI and superior colliculus, influence eye movement
vestibulospinal tracts
medial (C spinal cord) and lateral (limbs and trunk) tracts influence posture
vestibulocolic pathways
CN XI nucleus, influences head position
vestibulothalamocortical
conscious awareness of head position/movement and input to influence corticospinal tracts
vestibulocerebellar
controls magnitude of muscle responses to vestibular information
vestibuloreticular
reticulospinal tract influence and autonomic centers for nausea and vomiting
what is benign paroxysmal positional vertigo
acute onset vertigo and nystagmus following rapid head movement that subsides within 2 minutes
what causes benign paroxysmal positional vertigo
displacement of otoliths into a semicircular canal
movement causes abnormal flow of endolymph
what repositioning maneuvers are used for benign paroxysmal positional vertigo?
Dix-Hallpike - diagnosis
Epley - treatment
why are semicircular canals insensitive to gravitational orientation and linear acceleration under normal conditions?
because endolymph and the cupula have the same specific gravity
what is Ménière’s disease?
aka idiopathic endolymphatic hydrops
increased pressure of the endolymph system, causes expansion of the membranous labyrinth
what are the symptoms of Ménière’s disease
fluctuating hearing loss
occasional episodic vertigo
tinnitus
aural fullness
what does the taste system identify
nutrients/toxins ingested
what receives information from taste receptor cells? what do they do?
primary afferent nerve fibers receive info from taste receptor cells, encode the info as action potentials
taste pathway
CN VII, IX, X to rostral solitary nucleus
through central tegmental tract to ventral posterior medial nucleus
to gustatory cortex in insular and frontal operculum
what are the secondary projection neurons of the olfaction system
mitral and tufted cells
where do the secondary projection neurons synapse
in olfactory glomeruli
what does the anterior olfactory nucleus do
modulates info in the olfactory bulb, contains bilateral connections via medial olfactory stria
functions in early olfactory processing and feedback
what do the amygdala and olfactory tubercle do in the olfaction pathway?
emotional, endocrine, and visceral consequences of odors
what does the piriform cortex do
olfactory perception
what does the entorhinal cortex do
olfactory memories
